Page 281 - Whole Earth Geophysics An Introductory Textbook For Geologists And Geophysicists

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263 (Am), density in change com- topo- for used the of simplifying of depth of series rift then This the at starting bound- model grav- of lithosphere; models. grav- to result- three the in

Expressions mass in significant therefore: the to then is anomaly the for chosen commonly sum the these a at is depth. The (continental mid-ocean ridge), range). (mountain that, so model the for was three the composite Bouguer and the lithosphere thick other the contribution flat, are these to anomalies

Gravity /ateral changes of Zones (lithosphere/asthenosphere due air contrasts those therefore effects: Moho the km 180 apart 2.18. to each it as of depth craton. A air of version km 180 for boundaries depths in gravity

their to boundaries, are g/cm’. g/cm’. g/cm’. g/cm’. gravity free as is constructed-with level; 2) at is craton and fragments 2.14 in same in the of free a compensation topographic Changes to

and g/em3 due (Ap). +2.67 1.64 +0.4 s —0.04 to The Density same anomaly bathymetric sea the margins Figs. depth the is changes for forms simplified incorporates no contributions
Settings = 3.3 effects are boundaries (topography): = Pg (bathymetry): = (peu = (Pc), of lithosphere = Pm contributions calculated. the exactly Bouguer and craton, at is boundary ripping of continental in portrayed change pressure from zero to and a is of depth is lithosphere/asthenosphere contributions.

Tectonic g/em* g/em? g/cm? 3.26 across fundamental air — (p.)y — py (Moho): — pm py = — models, are contributions. are the topographic continental craton the progression (continental the boundaries the km), result equal amplitudes tectonic settings. 8.41 Fig. model standard so there level, negative

= 2.67 2.9 = of Lithosphere: p,, = p, modeling, important three vs. level = Ap upper crust = Ap = Ap mantle part Ap boundaries three effects 8.12): a of lithosphere/asthenosphere a basin colliding Cycle,” (180 gravity contribution the of The the sea and gravity or
(p,)y (p,), contrasts the vs. lower crust vs. five the (Fig. the with surface as ocean and “Wilson fundamental to different Craton craton. as at is Moho their positive

crust: crust: part Asthenosphere: density by effects: Mass above sea water vs. the of the of of sum bathymetric corrections without start the 1) viewed an ocean the compensation Contributions each to comparison the in continental chosen surface the to in result

Upper Lower Mantle gravity by bounded Shallow Ocean Mantle Asthenosphere boundary): each each the and models the be can opening the is three relative a Continental thus is form models.
reflected contrast, 1. 2. 3. depth puted graphic Bouguer km; 33 models zone), closing “ depth craton. aries, then ity stable a 180 The ity. ing in other
In a) b) For to as contributions The assumptions: 3) progression The of shows anomalies 1. km model Likewise, no boundaries

characteristic litho- entire nor- of continental and crust the and crust con- can basin ocean sides the on lithosphere, a as crust simi- are expressions significant conti- a for compensation illus- to grav- ridges). the on relief than dense column lithosphere of part mantle crustal and boundary example. for to 1994). al.. et excess mass equi- isostatic compen-

has and crust lithosphere lithosphere. thicker oceanic the rifting b) an forming margins oceanic the of 8.40) (Fig. gravity no be may said be sufficient settings. mid-ocean considering less is asthenosphere the of the lithosphere/asthenosphere topography the Alps. balance, contributing 30 Lillie a comprises of due settings.
Equilibrium setting Each the of and crust thin and from ocean; thin apart rips 2.13); (Fig. created, continental the of thickening model the respective there old, can same isostasy. where often is 8.20). three those rifts: without asthenosphere the 1) part mantle and the to due lithosphere/asthenosphere In anomalies. 1983: al., et models as well 1975). anomalies

Isostatic settings. thicknesses Jevel; sea crust transition normal than crust. thick craton a as zone rift is lithosphere passive subduction and margins on range 8.32, 8.36). Their are features boundary. The Airy normal (Fig. Moho in anomalies (continental adequately the that that: so the to asthenosphere the on relief excesses 3 the gravity of isostatic (Kissling downgo

Local tectonic and near topography; thin topography; water topography; a) that: continental and center through continental mountain those assuming deepest Bouguer divergence Note lithosphere, relative between large mass settings, modeling component anomalies the of gravity and (Grow contributions (bathymetry),

lsostasy in five (bathymetry) Topography in Drop Shallower in a forming oceanic the close 2.18). and (Figs. models when the and explained boundary. the of (—Am), contrast that so compensate plate in important gravity mantle in for flexure show simplified g/cm*

and Regions comprise Craton: Uplifted Margin: crust. High related, new in can basin the of (Fig, margin lithosphere/asthenosphere modeling of plate be part small, to considered an the accounted below topography for 1.03
Gravity for below topography thickness. Rift: oceanic Ridge: lithosphere. Range: are settings thin. where point ridge the collision forms continental previous because Gravity depth the of free-air active of cannot mantle deficit mass density is required convergent be is root observed zones, be lithosphere models in depth, are: 0 = = p,

8 Anomalies models of Continental mal Continental Continental thinner Mid-Ocean thin Mountain The lithosphere the mid-ocean c) 2.14); in range The in those similar, the craton. at forms areas anomalies lithosphere/asthenosphere overlying, the 2) lithosphere is active to needs lithosphere the to subduction to needs and The changes boundary p, Air: Water:
Chapter The heights sphere. 1. ai od to 4. 5. entire to tinue a with (Fig. resulting mountain to lar also are on relief nental achieved is the trate In ity the represents (+Am); the boundary thinning. In also a mGal 50 At that librium satory sphere assumptions

262 Gravity